Down-the-hole drill assembly

Abstract

The invention provides a down-the-hole drill assembly having exhaust passages from upper and lower chambers past the inner end of a bit and through the body of the bit to exit through the bit face. The construction of the assembly and bit obviates a foot valve tube from the head of the bit and the disadvantages associated with this component.

1. A down-the-hole drill assembly having a reciprocating piston with a bore extending therethrough, a length of the bore being inwardly stepped to snugly receive a closed end pressurized air distributor tube having an apertured sidewall, an upper chamber for pressurized air to cause downward travel of the piston, a lower chamber for pressurized air to cause the piston to lift and a drill bit with an inner end, body and face, the inner end of the bit being closed and exhaust passages being provided from the upper and lower chambers past the inner end of the bit and through the body of the bit to exit through the bit face, wherein the piston is movable between a driving position in which the bore step is open and the distributor aperture is in flow communication with the piston bore, and a lifted position in which the bore step is closed by the distributor and the aperture is in flow communication with the upper chamber. 
   
   
     2. A drill assembly as claimed in  claim 1  wherein the exhaust passages exit via at least one vent extending through the bit body from the bit face. 
   
   
     3. A drill assembly as claimed in  claim 1  wherein the bit has openings extending transversely through the body of the bit into a blind bore extending from the bit face. 
   
   
     4. A drill assembly as claimed in  claim 3  wherein a flushing air orifice extends through the closed inner end of the bit.